The present invention relates generally to electrostatic discharge protection devices. More particularly, the invention relates to electrostatic discharge protection devices for semiconductor chip packages ("SCP") where the electrostatic discharge protection device connects pins on the SCP to inhibit electrostatic charge accumulation, and disconnects the ground connection upon operative combination of the SCP on the circuit board, or, optionally, disconnection can be a manual operation.
Electrostatic charge is a stationary electric charge which accumulates on various surfaces. An electrostatic discharge occurs when the electrostatic charge becomes substantial enough to overcome a dielectric material between the charge and another surface of lower electrical potential. An example of such a discharge as naturally occurring is lightning.
Electrostatic discharge in the realm of electronics can be devastating to microelectronic devices. A sharp voltage spike caused by an electrostatic discharge can cause permanent and costly damage to individual precision devices, such as random access memory or other semiconductor devices, inter alia.
Many commercially available electrostatic discharge protection devices in use today consist primarily of electrostatic discharge packaging of the SCP in electrically conductive strips, pellets, boxes, and plastic tubing which provide effective electrostatic discharge protection until the user is about to insert the SCP onto the circuit board. At that point the user must remove the electrostatic discharge packaging from the SCP thus rendering the SCP vulnerable to electrostatic discharge in order to position and insert the connector pins onto the circuit board. Accordingly, as the user inserts the connector pins of the SCP into the receptacles, the semiconductor dies housed within the SCPs could be destroyed by electrostatic discharge and the SCP would therefore have to be replaced.
In some instances, where the receptacle itself is electrostatically charged, it is advantageous to allow the electrostatic discharge protection device to remain in place and be removed manually.
Surface mount microelectronic devices have an additional problem in that they often have numerous small pins, often on all four sides of the SCP, thereby making the surface mount device difficult to handle. A prior art electrical connector receptacle arrangement is described in commonly assigned U.S. Pat. No. 5,108,299 entitled "Electrostatic Discharge Protection Devices for Semiconductor Chip Packages" by David V. Cronin issued Apr. 28, 1992. This patent shows a shunt attachment placed on pins of the semiconductor chip package arranged to provide a short circuit across selected pins. Upon insertion into the receptor, the attachment is driven away from the semiconductor chip package, causing the short circuit to be broken. While this arrangement is an improvement and is useful for connectors for semiconductor chip packages such as Dual In-line Packages, DIPs, the design requires that they be fairly large and clip to the semiconductor chip package which in the case of surface mount or other chips having pins on all four sides or numerous small pins, can become unwieldy.
Other commonly assigned patents and copending applications include U.S. Pat. No. 4,971,568 entitled "Electrical Connector With Attachment For Automatically Shorting Select Conductors Upon Disconnection of Connector" by David V. Cronin issued Nov. 20, 1990, U.S. Pat. No. 5,163,850 entitled "Electrostatic Discharge Protection Devices For Semiconductor Chip Packages" by David V. Cronin issued Nov. 17, 1992, U.S. Pat. No. 5,164,880 entitled "Electrostatic Discharge Protection Device for a Printed Circuit Board" by David V. Cronin issued Nov. 17, 1992, and pending U.S. application Ser. No. 08/234,917 now U.S. Pat. No. 5,490,033 entitled "Electrostatic Discharge Protection Device" by David V. Cronin filed Apr. 28, 1994.
In addition, the prior art electrostatic discharge protection devices often need downward pressure to release a ground connection, and upon release, the electrostatic discharge protection device causes a bias of the SCP away from its receptacle. While this is not a significant limitation if there is enough resistive or tractive force to hold the SCP in this position, this limitation, in the case of surface mount, does force the use of an adhesive to secure the SCP before soldering.
In the case of surface mount microelectronic devices, or other SCPs which have large quantities of connector pins, additional problems arise in the difficulty of manufacturing the prior art electrostatic discharge protection devices and a loss of rigidity of the electrostatic discharge protection devices over a long span. With respect to the latter, if the electrostatic discharge protection device has only two points of contact for a row of connecting arms, one on each end, a long span causes the middle of the row to lag the outer parts of the row when pulling away due to flex in the structure over the long span.
Accordingly, it is an object of this invention to provide electrostatic discharge protection devices which operate to automatically open a short between selected conductors upon connection with a mating receptacle or is adapted to manually open the short circuit if the mating receptacle is also subject to electrostatic discharge.
It is another object of this invention to provide electrostatic discharge protection devices that do not bias the SCP away from its receptacle.
It is still another object of the invention to provide an electrostatic discharge protection device which is easier and, therefore, less costly to manufacture.
These and other objects of the invention will be obvious and will appear hereinafter.